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Molecular definition of an elusive third HLA-A9 molecule: HLA-A9.3
A M Little1, J A Madrigal, P Parham
1Department of Cell Biology, Stanford University School of Medicine, CA 94305-5400.
Abstract:
The HLA-A9 family has been characterized as possessing two well defined specificities; HLA-A23 and A24. Serological studies have suggested the presence of a third member of this family HLA-A9.3, however there is doubt surrounding the existence of this specificity. HLA-A23, A24, and the putative A9.3 proteins were analyzed biochemically by immunoprecipitation and isoelectric focusing. Both HLA-A24 and A9.3 have identical isoelectric points whereas A23 is different. We have sequenced cDNA encoding HLA-A23, A24, and A9.3. From the observed protein sequences, we found A9.3 to differ from A24 by two amino acid substitutions located in the alpha 2 helix of the class I molecule. These substitutions are expected to significantly change the shape of the peptide binding cleft.